Dataset on investigating nucleation and growth kinetics of methane hydrate in aqueous methanol solutions.

This work systematically investigates the effect of methanol (MeOH) in a wide range of concentrations (0, 1, 2.5, 5, 10, 20, 30, 40, and 50 mass%) on methane hydrate nucleation and growth kinetics. Multiple measurements of gas hydrate onset temperatures and pressures for CH4-H2O and CH4-MeOH-H2O systems were performed by ramp cooling experiments (1 K/h) using sapphire rocking cell RCS6 apparatus. The dataset comprises 96 ramp experiments conducted under identical initial conditions for each solution (gas pressure of 8.1 MPa at 295 K). The reported hydrate onset temperatures and pressures range within 248-282 K and 6.2-7.5 MPa, respectively. The methane hydrate onset subcooling was calculated using literature data on the three-phase gas-aqueous solution-gas hydrate equilibrium for the studied systems. The study determined the numerical values of the shape and scale parameters of gamma distributions that describe the empirical dependences of methane hydrate nucleation cumulative probability as a function of hydrate onset subcooling in the aqueous methanol solutions. Gas uptake curves were analyzed to characterize the kinetics of methane hydrate growth under polythermal conditions at different methanol concentrations.

Data on searching for synergy between alcohol and salt to produce more potent and environmentally benign gas hydrate inhibitors.

In order to systematically study the synergistic effect of gas hydrate inhibition with mixtures of methanol (MeOH) and magnesium chloride (MgCl2), the impact of these compounds on the thermodynamic stability of methane hydrate in the systems of CH4-MeOH-H2O, CH4-MgCl2-H2O, and CH4-MeOH-MgCl2-H2O was experimentally investigated. The pressure and temperature conditions of the three-phase vapor-aqueous solution-gas hydrate equilibrium were determined for these systems. The resulting dataset has 164 equilibrium points within the range of 234-289 K and 3-13 MPa. All equilibrium points were measured as the endpoint of methane hydrate dissociation during the heating stage. The phase boundaries of methane hydrate were identified for 8 systems with MeOH (up to 60 mass%), 5 MgCl2 solutions (up to 26.7 mass%), and 14 mixtures of both inhibitors. Most equilibrium points were measured using a ramp heating technique (0.1 K/h) under isochoric conditions when the fluids were stirred at 600 rpm. It was found that even a 0.5 K/h heating rate for the CH4-MgCl2-H2O system at low salt concentrations, along with all mixed aqueous solutions with methanol, gives results that do not differ from 0.1 K/h, considering the measurement uncertainties. Most measurements for the CH4-MgCl2-H2O system at high salt content were acquired using a step heating technique. The coefficients of the empirical equations approximating the equilibrium points for each inhibitor concentration were defined. The change in the slope parameter of the empirical equation was analyzed as a function of inhibitor content. Correlations that accurately describe the thermodynamic inhibition effect of methane hydrate with methanol and magnesium chloride on a mass% and mol% scale were obtained. The freezing temperatures of single and mixed aqueous solutions of methanol and magnesium chloride were determined experimentally to confirm the thermodynamic consistency of the methane hydrate equilibrium data.

Dataset for the new insights into methane hydrate inhibition with blends of vinyl lactam polymer and methanol, monoethylene glycol, or diethylene glycol as hybrid inhibitors.

Three-phase equilibrium conditions of vapor-aqueous solution-gas hydrate coexistence for the systems of CH4-H2O-organic thermodynamic inhibitor (THI) were experimentally determined. Hydrate equilibrium measurements for systems with methanol (MeOH), monoethylene glycol (MEG), and diethylene glycol (DEG) were conducted. Five concentrations of each inhibitor (maximum content 50 mass%) were studied in the pressure range of 4.9-8.4 MPa. The equilibrium temperature and pressure in the point of complete dissociation of methane hydrate during constant-rate heating combined with vigorous mixing of fluids (600 rpm) in a high-pressure vessel were determined. We compared our experimental points with reliable literature data. The coefficients of empirical equations are derived, which accurately describe hydrate equilibrium conditions for the studied systems. The effect of THI concentration and pressure on methane hydrate equilibrium temperature suppression was analyzed. In the second stage, we studied the kinetics of methane hydrate nucleation/growth in systems containing a polymeric KHI (0.5 mass% of N-vinylpyrrolidone and N-vinylcaprolactam copolymer) in water or THI aqueous solution. For this, temperatures, pressures, and subcoolings of methane hydrate onset were measured by rocking cell tests (RCS6 rig, ramp cooling at 1 K/h). Gas uptake curves characterizing the methane hydrate crystallization kinetics in the polythermal regime were obtained.

Dataset for the dimethyl sulfoxide as a novel thermodynamic inhibitor of carbon dioxide hydrate formation.

The temperatures and pressures of the three-phase equilibrium V-Lw-H (gas - aqueous solution - gas hydrate) were measured in the CO2 - H2O - dimethyl sulfoxide (DMSO) system at concentrations of organic solute in the aqueous phase up to 50 mass%. Measurements of CO2 hydrate equilibrium conditions were carried out using a constant volume autoclave by continuous heating at a rate of 0.1 K/h with simultaneous stirring of fluids by a four-blade agitator at 600 rpm. The equilibrium temperature and pressure of CO2 hydrate were determined for the endpoint of the hydrate dissociation in each experiment. The CO2 gas fugacity was calculated by the equation of state for carbon dioxide for the measured points. The flow regime in the autoclave during the operation of the stirring system was characterized by calculating the Reynolds number using literature data on the viscosity and density of water and DMSO aqueous solutions. We employed regression analysis to approximate the dependences of equilibrium pressure (CO2 gas fugacity) on temperature by two- and three-parameter equations. For each measured point, the value of CO2 hydrate equilibrium temperature suppression ΔTh was computed. The dependences of this quantity on CO2 gas fugacity are considered for all DMSO concentrations. The coefficients of empirical correlation describing ΔTh as a function of the DMSO mass fraction in solution and the equilibrium gas pressure are determined. This article is a co-submission with a paper [1].